-(defstruct timer (start 0) (paused 0) (state 'stopped))
-
-(defun start-timer (timer)
- (setf (timer-start timer) (SDL_GetTicks))
- (setf (timer-state timer) 'running))
-
-(defun stop-timer (timer)
- (setf (timer-state timer) 'stopped))
-
-(defun get-time (timer)
- (cond ((eq (timer-state timer) 'stopped) 0)
- ((eq (timer-state timer) 'paused) (timer-paused timer))
- (t (- (SDL_GetTicks) (timer-start timer)))))
-
-(defun pause-timer (timer)
- (cond ((eq (timer-state timer) 'running)
- (setf (timer-paused timer) (- (SDL_GetTicks) (timer-start timer)))
- (setf (timer-state timer) 'paused))))
-
-(defun resume-timer (timer)
- (cond ((eq (timer-state timer) 'paused)
- (setf (timer-start timer) (- (SDL_GetTicks) (timer-paused timer)))
- (setf (timer-state timer) 'running))))
-
+(define (make-timer)
+ '((start . 0) (paused . 0) (state . stopped)))
+
+(define (start-timer timer)
+ (assoc-set! timer 'start (SDL_GetTicks))
+ (assoc-set! timer state 'running))
+
+(define (stop-timer timer)
+ (assoc-set! timer 'state 'stopped))
+
+(define (get-time timer)
+ (cond ((eq? (assoc 'state timer) 'stopped) 0)
+ ((eq? (assoc 'state timer) 'paused) (assoc 'paused timer))
+ (else (- (SDL_GetTicks) (assoc 'start timer)))))
+
+(define (pause-timer timer)
+ (cond ((eq? (assoc 'state timer) 'running)
+ (assoc-set! timer 'paused (- (SDL_GetTicks) (assoc 'start timer)))
+ (assoc-set! timer 'state 'paused))))
+
+(define (resume-timer timer)
+ (cond ((eq? (assoc 'state timer) 'paused)
+ (assoc-set! timer 'start (- (SDL_GetTicks) (assoc 'paused timer)))
+ (assoc-set! timer 'state 'running))))